multiple functions that contribute to their evasion strategy. Retrovirally produced structural proteins have been shown to interact with hundreds of host factors. Some of these interactions are required for successful virus replication, while others may be important for retroviral evasion of the host response. These ‘extrastructural’ roles of structural proteins could be activated/regulated in a specific manner to exhibit an immune evasion function. Post-translational modifications could, for example, result in an increased protein interactome for some retroviral proteins. Phosphorylation might change the structure of Gag to counteract a host-restriction factor in a simple retrovirus, whereas in a complex retrovirus, a new gene might be acquired to accomplish the same evasion mechanism. Endosomal acidification may cause conformational changes in viral capsid proteins enabling them to bind to host factors to withstand an antiviral response. A deeper understanding of how retroviruses utilize their genome for immune evasion will lead to the identification of overlooked evasion strategies and novel functions for viral proteins. It is also possible that retroviruses exploit microorganisms to evade the host response. Like many pathogens, retroviruses have evolved in the context of the commensal microflora of their hosts. One can hypothesize that retroviruses may take advantage of the commensals (i.e., as adjuvant) by tolerizing the host and, thus, suppressing the antivirus immune response. Incredibly, this evasion route requires no virulence factors to achieve the intended purpose. Gnotobiotic models should be used to discern the role of normal flora in retroviral evasion.
How is retroviral infection sensed?

“A deeper understanding
of how retroviruses utilize their genome for immune evasion will lead to the identification of overlooked evasion strategies and novel functions for viral proteins.”

An adaptive immune response against a pathogen begins with recognition of pathogen-associated molecular patterns by the pattern-recognition receptors of the innate immune system [2,3] .
Future Virol. (2010) 5(1), 5–6
ISSN 1746-0794

part of

5

IL 60637. but also against the future retroviruses that we are certain to encounter.edu
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6
Future Virol. Most viruses utilize numerous immune-evasion mechanisms. Knowledge gained from these studies will lead to development of vaccines that could recapitulate a live-virus vaccine without using live virus. Department of Microbiology. Rev. genomic RNA and reverse transcriptase are packaged and the virus egresses from the cell. 766–775 (2009). Adv. or recognizing nucleic acids in a cellular compartment where they are normally absent (i. establishing a provirus. Chicago. Nat. Med.
2. Cell Host Microbe 3. 3. This is important for producing prophylactic vaccines.
Financial & competing interests disclosure
This work was supported by PHS grant CA113784 to Tatyana V Golovkina. Opin.
5. termed the capsid [5] . viral RNA molecules transcribed from the integrated provirus are translated to produce the viral proteins.Editorial
Golovkina & Yurkovetskiy
Pattern-recognition receptors sense replicative intermediates of viruses by recognizing structures not normally found in the host cell. Further studies should be aimed at determining mechanisms responsible for recognition of retroviral pathogens and virally evolved mechanisms to block this detection. Pasare C. Department of Microbiology. During transport to the nucleus. not only against HIV.
Malim MH.e. Chicago.: +1 773 834 1073 Fax: +1 773 834 8150 leonidy@uchicago. This raises the questions of what the retroviral pathogen-associated molecular patterns are and how they are sensed. USA Tel.. 920 East 58th street. However. Curr. 11–18 (2005).
Tatyana V Golovkina Associate Professor. Emerman M: HIV-1 accessory proteins – ensuring viral survival in a hostile environment. 920 East 58th street. such as dsRNA. These events expose the virus to endosomal and cytosolic innate immune receptors. 244–250 (2009). second. Biol.: +1 773 834 7988 Fax: +1 773 834 8150 tgolovki@bsd.
with similar forms made by the host. including different nucleic acid forms. Stetson DB: Connections between antiviral defense and autoimmunity. Immunol. USA Tel. deficiencies in specific adaptive or innate immune pathways result in increased retroviral titers and. retroviruses have evolved numerous mechanisms to avoid immune recognition. IL 60637. (2010) 5(1)
future science group
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Affiliations
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4.edu Leonid Yurkovetskiy Predoctoral Trainee.
Conclusion & future perspective
Pathogens that cause chronic infections excel in adapting to the host in a manner that ensures long-term residence. University of Chicago. producing dsDNA molecules. infection with retroviruses rarely leads to an immune response that can prevent ongoing virus replication. Medzhitov R: Toll-like receptors: linking innate and adaptive immunity. RNA/DNA in endosomes and DNA in the cytosol). suggesting that they evolved highly efficient mechanisms to escape an immune attack. but are still eliminated or efficiently controlled by the immune system. Two observations indicate that the immune response exerts extensive pressure on retroviral replication. These detection events are then translated into a pathogen-specific adaptive immune response [4] . 5. Various replication intermediates. which are subsequently integrated into the infected cell’s genome. Immunity 30. First. could potentially be targeted by the innate immune system as they might have physical/structural or subcellular localization differences compared
Bibliography
1. After integration. University of Chicago. Goff SP: Host factors exploited by retroviruses.uchicago. 21. 388–398 (2008). No writing assistance was utilized in the production of this manuscript. by mimicking natural detection events and subsequent adaptive immune responses. Clearly.
Medzhitov R: Approaching the asymptote: 20 years later. Retroviruses are enveloped viruses with the genomic RNA packaged within a protein shell. 560. we know little about the initial events that lead to host recognition of retroviral pathogens. Microbiol. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed. reverse transcription occurs in the preintegration complex. Retrovirus entry is mediated through the interaction of its Env protein with a surface receptor. As viral particles are being formed. 253–263 (2007). Exp.